Back-UPS CS 500 immediately switches off when battery+load

tagq2_apc · ‎2021-06-29

Hello, decade-old Back-UPS CS 500 which up to recently provided a couple of minutes runtime for a low power home server, i.e. enough to do a quick shutdown. This was until a couple of days ago: lost power; switched on monitor to check console status; power immediately lost. Thought battery had probably run down, but leaving it to charge for 24 hours now gives less than a second on battery back-up with even a 10-20W load. If no load, orange light will stay on for a little while.

Was thinking of getting only a new battery, but since the UPS isn't even reporting a dead battery, is this a symptom of problem with UPS itself? Anything I should try? (Yes, I know it's probably time to get a new one anyway because of age, but I'm still curious as to what might be up before just deciding to recycle the whole unit.) Thanks.

tagq2_apc · ‎2021-06-29

Hello, decade-old Back-UPS CS 500 which up to recently provided a couple of minutes runtime for a low power home server, i.e. enough to do a quick shutdown. This was until a couple of days ago: lost power; switched on monitor to check console status; power immediately lost. Thought battery had probably run down, but leaving it to charge for 24 hours now gives less than a second on battery back-up with even a 10-20W load. If no load, orange light will stay on for a little while.

Was thinking of getting only a new battery, but since the UPS isn't even reporting a dead battery, is this a symptom of problem with UPS itself? Anything I should try? (Yes, I know it's probably time to get a new one anyway because of age, but I'm still curious as to what might be up before just deciding to recycle the whole unit.) Thanks.

See Answer In Context

tagq2_apc · ‎2021-06-29

Thanks for the info on the self-test. The battery is 8+ years old, so it's impressive it was functioning even recently, I guess! Ignored it plugged in with no load for a few days, and noticed it can power a lamp for at least 20-30s now... anyway...

OK, looking around the options for new UPS. Is there any advantage to the "SC420I Smart-UPS 420VA" vs the "Back UPS RS LCD 550" (which appears to have higher rating, nice LED front panel and more inputs)? For example, does the former put out a smoother sine wave (meaning I can perhaps protect aquarium filter too...), or does that only apply to the higher end Smart-UPS? Cheers.

BillP · ‎2021-06-29

Well, Smart UPS SC and Back UPS RS LCD models both output a step approximated sinewave. The main difference is lack of fancy LCD on the SC420I and also the fact that SC420I provides serial communication along with USB. These are geared towards power users or small servers that require serial communication. The Back UPS LCD units are more geared towards consumers so they only provide USB connectivity.

Another option you might want to check is the Smart UPS C models (SMC). They provide pure sinewave output and are the replacements for the SC products, such as SC420I. They have an LCD as well, similar to the Back UPS LCD. For Smart UPS C though, it looks like the smallest one in the sense of VA capacity is SMC1000I that would work for you.

tagq2_apc · ‎2021-06-29

Hello, decade-old Back-UPS CS 500 which up to recently provided a couple of minutes runtime for a low power home server, i.e. enough to do a quick shutdown. This was until a couple of days ago: lost power; switched on monitor to check console status; power immediately lost. Thought battery had probably run down, but leaving it to charge for 24 hours now gives less than a second on battery back-up with even a 10-20W load. If no load, orange light will stay on for a little while.

Was thinking of getting only a new battery, but since the UPS isn't even reporting a dead battery, is this a symptom of problem with UPS itself? Anything I should try? (Yes, I know it's probably time to get a new one anyway because of age, but I'm still curious as to what might be up before just deciding to recycle the whole unit.) Thanks.